Last week China was preparing to start assembling its own space station. After the successful launch of the first part of the station, the rocket that carried it into orbit is about to return to Earth. But it will return uncontrolled, becoming one of the largest objects to re-enter in an uncontrolled manner.
According to Aerospace, the rocket is expected to re-enter the atmosphere on May 10 at 01:00 GMT. However, with a window of approximately 41 hours. Based on the trajectory the rocket is following and with its orbital inclination of 41.5 degrees, it could fall as far north as Madrid and as far south as New Zealand.
What is expected to fall uncontrollably is the center stage of the Long March 5B rocket, the one that carried the first part of the Tianhe space station into orbit. It is about 50 meters high and 5 meters wide, making it one of the largest objects expected to re-enter the Earth in an uncontrolled manner. It weighs approximately 20 metric tons.
Initially it was planned that the core stage would return to Earth after orbiting the station and land at a controlled location. However, something happened after orbiting the space station and instead of returning, it got stuck in Earth’s orbit.
Is this dangerous? In principle it need not be. Once the rocket starts to enter the atmosphere it will burn up and end up in pieces before it hits the ground. However, because of how big it is and because it falls in an uncontrolled manner, there is a slim chance that some debris will manage to reach the surface, in populated areas.
Normally space agencies perform special maneuvers with the objects they drop back to Earth. With these maneuvers they manage to control the re-entry so that it burns up as much as possible or falls into oceans and unpopulated areas. However, data collected with devices from Earth shows that the Long March 5B core stage is falling out of control.
Until the rocket’s re-entry is confirmed, it will be impossible to determine more precisely where it will fall and whether there will be debris reaching the surface.
Objects of such size have very rarely re-entered in an uncontrolled manner. The last one to overcome it was the Russian Salyut 7 spacecraft, which weighed 39 metric tons and ended up over Argentina in 1991. The largest object to cause an uncontrolled re-entry was the 79-ton U.S. Skylab station over the Indian Ocean and Western Australia in 1979.